250  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [buli..S6' 
wesl  coast  of  Trinity  bay  arc  correlated  with  the  Huroniau  on  litholog- 
ical  evidence.  The  rocks  here  are  in  some  respects  different  from  those 
on  St.  Johns  peninsula,  bnt  this  difference  seems  to  be  due  to  the  in- 
tense volcanic  activity  which  has  affected  the  western  part  of  Avalon. 
Dikes  of  various  kind  intersect  the  formation,  and  the  strata  arc  in 
places  volcanic  conglomerates,  volcanic  ashes,  etc.  The  rocks  of  Brigne, 
described  in  the  report  for  1868,  are  found  to  contain  several  beds  which 
are  crowded  with  Aspidella. 
Murray,73  in  1873,  finds  gneissic  rocks  at  several  localities  in  St. 
Georges  bay.  Associated  with  these  are  labradorite  and  other  anortho 
site  rocks  which  belong  to  the  upper  Lanrentian  system.  Also,  on  the 
Great  Oodroy  river  is  found  white  crystalline  limestone  with  graphite, 
which  is  regarded  as  a  further  indication  of  the  presence  of  this  divi- 
sion of  the  Lanrentian. 
Murray,74  in  1875,  finds  on  Gander  lake  micaceous  slate,  fine  grained 
granite,  and  gneiss,  which  are  correlated  with  the  Lanrentian  gneiss  of 
Bona  vista  bay. 
Howley,75  in  1877,  further  examines  Gander  lake  and  river  and  finds 
chlorite- slates,  diorites,  and  mica-slates  which  contain  no  organic  remains, 
and  which  on  account  of  their  lithological  character  and  the  serpentine 
they  contain  are  provisionally  placed  with  the  Quebec  group.  Upon 
the  upper  Gambo  pond  and  Riverhead  brook  are  found  sandstones  and 
quartzites  which  at  some  places  pass  almost  imperceptibly  into  gneiss, 
which  rocks,  with  the  associated  micaceous  slates,  are  provisionally 
placed  with  the  Huronian. 
Howley,™  in  188-},  further  describes  the  intermediate  system  of  Hu- 
roniau rocks.  These  metamorphic  rocks  occupy  the  greater  part  of  the 
peninsula  of  Avalon.  They  rest  upon  a  nucleus  of  Lanrentian  gneiss 
and  are  succeeded  by  fossiliferous  beds  of  the  Primordial  age  which 
skirt  the  shores  of  the  bays  and  are  found  to  rest  unconformably  on 
the  basset  edges  of  the  upturned  and  altered  Huroniau,  and  occasion- 
ally in  contact  with  the  still  older  Lanrentian.  The  intermediate  rocks 
are  found  to  be  gently  folded  so  that  the  same  strata  are  repeated  sev- 
eral times.  Associated  with  these  Huroniau  rocks  are  trappean  beds 
and  volcanic  ash.  Contained  in  them  are  found  two  fossils,  Aspidella 
terranovioa  and  Arenicolites  spirales.  This  latter  fossil  is  said  tooccur 
in  the  Primordial  rocks  of  Sweden.  These  fossils  give  important 
assistance  in  the  ready  recognition  of  the  Huronian.  The  gneissic 
rocks  which  have  been  described  as  being  members  of  the  Lanrentian 
system  protrude  through  the  Huroniau  strata  by  which  they  are  sur- 
rounded. Gutting  the  Huroniau  rocks  is  found  a  series  of  granitoid 
and  other  plutonic  rocks  which  obliquely  intersect  the  eastern  part  of 
the  peninsula,  including  the  Laurentian  gneiss.  A  second  great  igne- 
ous intrusion  cuts  all  of  the  rocks  of  the  western  part  of  the  peninsula, 
including  the  Potsdam  sandstone.  The  intrusions  of  the  eastern  pe'- 
ninsula  are  taken  to  be  of  older  date  than  the  trap  of  the  western  penin 
